Noble metal single atom supported three-way catalyst and preparation method therefor and use thereof

Abstract

The present invention relates to a preparation method for a noble metal single atom three-way catalyst, a catalyst obtained by using the method, and a use of the catalyst for purifying motor vehicle exhaust gas. In the present invention, a nitrogen-containing compound is used for treating a noble metal single atom catalyst precursor, avoiding the agglomeration of noble metal single atoms into nanocrystalline particles. The catalyst obtained by the preparation method of the present invention is resistant to high temperature, is not prone to agglomerate, and is resistant to poisoning, and the amount of usage of noble metals is reduced while the purification efficiency of the catalyst for motor vehicle exhaust gas is effectively improved.

1 . A preparation method of a noble metal single-atomic supported three-way catalyst, comprising:
 Step A: loading a noble metal precursor in a designed load amount on an oxide support to form a noble metal single-atomic catalyst precursor;   Step B: using a nitrogen-containing compound to treat the noble metal single-atomic catalyst precursor;   Step C: calcining the noble metal single-atomic catalyst precursor treated with the nitrogen-containing compound as obtained in Step B, to obtain the noble metal single-atomic supported three-way catalyst;   the noble metal precursor is a soluble noble metal inorganic salt, or a noble metal organic salt, or a noble metal complex; alternatively, the noble metal precursor is nitrate, chloride, sulfate, acetate, acetylacetonate or chlorine complex; and the soluble means soluble in water or alcohol, wherein the alcohol is methanol or ethanol;   in the noble metal single-atomic supported three-way catalyst, the noble metal is dispersed in the state of single-atomic sites on the oxide support, wherein the noble metal is one, or a combination of two or more of platinum, palladium, rhodium, ruthenium, iridium, osmium, gold and silver;   the oxide support is alumina, silica-alumina, ceria-zirconia mixed oxide, or molecular sieve, or a mixture of any two or more thereof, and optionally doped with BaO, La 2 O 3  and/or Y 2 O 3 ; or the oxide support is a mixed oxide of Al 2 O 3  and Zr—Ce-M-O x  oxide, wherein M is one or more selected from the group consisting of Ba, Sr, La, Y, Pr, Nd;   the nitrogen-containing compound is NH 3 , dimethylformamide, urea, C 1-20  alkane amine, C 2-20  alkene amine, C 1-20  alkane diamine, C 1-20  alkane triamine, or C 6-20  aromatic amine; alternatively, the nitrogen-containing compound is NH 3 , dimethylformamide, urea, C 1-6  alkane amine, C 1-6  alkane diamine, or C 6-20  aromatic amine; alternatively NH 3 , ethylenediamine, triethylamine, n-butylamine or dimethylformamide; optionally an aqueous or alcoholic solution of the nitrogen-containing compound can be used, wherein the alcoholic solution is a methanol or ethanol solution.   
     
     
         2 . The preparation method according to  claim 1 , wherein, in the step A, mixing the oxide support with a noble metal salt solution, and separating the mixture to obtain a noble metal supported catalyst precursor; in the step B, using a nitrogen-containing compound to soak or wash the noble metal single-atomic catalyst precursor, and then undergoing solid-liquid separation to obtain a solid catalyst precursor; before the step C, drying the solid catalyst precursor as required; and in the step C, calcining at 200-600° C., or at 300-500° C. 
     
     
         3 . The preparation method according to  claim 1 , wherein the noble metal salt is a nitrate, chloride, acetate, acetylacetonate or chlorine complex of noble metal; the noble metal is platinum, rhodium, palladium or iridium, or a combination of two or more thereof, the content of the noble metal is 0.01-5 wt %, or 0.05-2 wt %, based on the weight of the catalyst. 
     
     
         4 . The preparation method according to  claim 1 , wherein the oxide support is a mixed oxide of Al 2 O 3  and Zr—Ce-M-O x  oxide, in this mixed oxide, where a the content of Al 2 O 3  is 15-80 wt %, the content of Zr—Ce-M-O x  is 20-85 wt %; the nitrogen-containing compound is an aqueous ammonia with a concentration of 0.5-15 wt %, or an aqueous solution of ethylenediamine with a concentration of 0.5-15 wt %, alternatively an aqueous ammonia or an aqueous solution of ethylenediamine with a concentration of 0.5-5 wt %. 
     
     
         5 . A method for preparing a noble metal single-atomic three-way catalyst, comprising:
 Step 1: using a nitrogen-containing compound to treat a noble metal single-atomic catalyst precursor;   Step 2: calcining the noble metal single-atomic catalyst precursor treated with the nitrogen-containing compound to obtain the noble metal single-atomic three-way catalyst;   in the noble metal single-atomic catalyst precursor, the noble metal is dispersed in the state of single-atomic sites on a support; the noble metal is selected from the group consisting of platinum, palladium, rhodium, ruthenium, iridium, osmium, gold, silver, and the noble metal is a single one thereof, or a combination of two thereof, or combination of more thereof;   the support is alumina, silica-alumina, ceria-zirconia mixed oxide, or molecular sieve or a mixture of any two or more thereof, and optionally doped with BaO, La 2 O 3 , Y 2 O; or the support is a mixed oxide of Al 2 O 3  and Zr—Ce-M-O x  oxide, wherein M is one or more selected from the group consisting of Ba, Sr, La, Y, Pr, Nd, and in the mixed oxide, the content of Al 2 O 3  is 15-80 wt %, and the content of Zr—Ce-M-O x  is 20-85 wt %;   the nitrogen-containing compound is NH 3 , dimethylformamide, urea, C 1-20  alkane amine, C 2-20  alkene amine, C 1-20  alkane diamine, C 1-20  alkane triamine or C 6-20  aromatic amine alternatively, the nitrogen-containing compound is NH 3 , dimethylformamide, urea, C 1-6  alkane amine, C 1-6  alkane diamine or C 6-20  aromatic amine; alternatively, the nitrogen-containing compound is NH 3 , ethylenediamine, triethylamine, n-butylamine or dimethylformamide; optionally, an aqueous or alcoholic solution of the nitrogen-containing compound can be used, wherein the alcoholic solution is a methanol or ethanol solution.   
     
     
         6 . The method according to  claim 5 , wherein in the step 1, using the nitrogen-containing compound to soak or wash the noble metal single-atomic catalyst precursor, then undergoing solid-liquid separation to obtain the noble metal single-atomic catalyst precursor treated with the nitrogen-containing compound; before the step 2, drying the noble metal single-atomic catalyst precursor treated with the nitrogen-containing compound as required; and in the step 2, calcining at 200-600° C., or at 300-500° C. 
     
     
         7 . The method according to  claim 5 , wherein the content of the noble metal is 0.01%-5%, or 0.05-2%, based on the weight of the catalyst; the support is a mixed oxide of Al 2 O 3  and Zr—Ce-M-O x  oxide, wherein M is one or more selected from the group consisting of Ba, Sr, La, Y, Pr, Nd, in the mixed oxide, the content of Al 2 O 3  is 15-80 wt %, and the content of Zr—Ce-M-O x  is 20-85 wt %. 
     
     
         8 . The method according to  claim 5 , wherein the nitrogen-containing compound is an aqueous ammonia with a concentration of 0.5-15 wt %, or an aqueous solution of ethylenediamine with a concentration of 0.5-15 wt %, alternatively an aqueous ammonia with a concentration of 0.5-5 wt % or an aqueous solution of ethylenediamine with a concentration of 0.5-5 wt %. 
     
     
         9 . A method for purifying motor vehicle exhaust, comprising using the noble metal single-atomic three-way catalyst prepared by the method according  claim 1  to purify a motor vehicle exhaust, wherein the catalyst is used alone or used by coating it on a honeycomb carrier for purifying the motor vehicle exhaust; wherein the honeycomb carrier is an alloy honeycomb carrier and/or a ceramic honeycomb carrier. 
     
     
         10 . A noble metal single-atomic three-way catalyst, wherein the is prepared by the method according to  claim 1 , the noble metal is platinum, rhodium, palladium, or iridium or a combination of two or more thereof, the content of the noble metal is 0.01-5 wt %, or 0.05-2 wt % based on the weight of the catalyst; the oxide support is a mixed oxide of Al 2 O 3  and Zr—Ce-M-O x  oxide, wherein M is one or more selected from the group consisting of Ba, Sr, La, Y, Pr, Nd, in the mixed oxide, the content of Al 2 O 3  is 15-80 wt %, the content of Zr—Ce-M-O x  is 20-85 wt %, wherein, the noble metal is dispersed in the state of single-atomic sites on the oxide support. 
     
     
         11 . A method for purifying motor vehicle exhaust, comprising using the noble metal single-atomic three-way catalyst prepared by the method according to  claim 5  to purifying a motor vehicle exhaust, wherein the catalyst is used alone or used by coating it on a honeycomb carrier for purifying the motor vehicle exhaust; the honeycomb carrier is an alloy honeycomb carrier and/or a ceramic honeycomb carrier. 
     
     
         12 . A noble metal single-atomic supported three-way catalyst by the method according to  claim 5 , the noble metal is platinum, rhodium, palladium, or iridium or a combination of two or more thereof, the content of the noble metal is 0.01-5 wt %, or 0.05-2 wt % based on the weight of the catalyst; the support is a mixed oxide of Al 2 O 3  and Zr—Ce-M-O x  oxide, wherein M is one or more selected from the group consisting of Ba, Sr, La, Y, Pr, Nd, in the mixed oxide, the content of Al 2 O 3  is 15-80 wt %, the content of Zr—Ce-M-O x  is 20-85 wt %, wherein, the noble metal is dispersed in the state of single-atomic sites on the oxide support.